There has been proposed an optical card system in which an optical card available for optically writing information therein by means of, for example, a laser light beam is used for recording information and information written on the optical card is reproduced from the optical card by, for example, a laser light beam.
In the optical card system proposed previously and disclosed in, for example, Japanese patent application published before examination under publication No. 60-229244, the optical card on which tracking guides are formed in a predetermined pattern is loaded on an optical card recording and reproducing apparatus. In the optical card recording and reproducing apparatus, the tracking guides provided on the optical card are detected and a position on the optical card upon which a light beam impinges is controlled in accordance with the tracking guides so that a tracking servo control of the light beam is carried out. Then, with the light beam subjected to the tracking servo control, writing of information on the optical card and reading of information from the optical card are performed. Further, in the optical card system proposed previously, the optical card is provided with address data recorded thereon beforehand, and the optical card recording and reproducing apparatus is operative to detect a position on the optical card in which information is to be written based on the address data read from the optical card and to write the information in the detected position on the optical card.
In the optical card recording and reproducing apparatus used in the optical card system previously proposed as mentioned above, an error signal for the tracking servo control of the light beam is produced based on the tracking guides provided beforehand on the optical card and detected from the optical card. Further the address data recorded beforehand on the optical card are read from the optical card to form reproduced address data when information is written in the optical card. Generally, the tracking guides are formed on the optical disc with, for example, a number of minute dots, each of which has a width of about 10.mu.. The address data are recorded on the optical disc by aligning a number of minute dots each having a width of about 10.mu.. The results is that the optical card recording and reproducing apparatus is required to read the minute dots for performing the tracking servo control of the light beam and for detecting the position on the optical card on which the information is to be written. Such reading of the minute dots by the optical card recording and reproducing apparatus easily receives a bad influence from scratches, dust or fingerprints on the surface of the optical card. Consequently, it is feared that the detection of the tracking guides and the reading of the address data from the optical card are not conducted accurately. Therefore, the tracking control of the light beam and the detection of the position at which the information is to be written are not carried out properly in the optical card recording and reproducing apparatus, making the optical card hard to handle.